A common route for the administration of pharmacologically active agents is a plurality of oral dosage forms; including such familiar forms as tablets, pills, and capsules. Such dosage forms are generally convenient, stable in storage and transport, and familiar to the user. However, they are not without problems, and these problems are often significant. It is extremely difficult for most people to swallow any of these oral dosage forms without supplemental water. In the fast-paced world, it is frequently inconvenient or messy to have to take supplementary water with oral medicaments. Such difficulties are compounded for those with difficulty in swallowing, such as, for example, children and the elderly. Certain medical conditions, such as Parkinsonism or other neurological states, make it difficult to swallow oral dosage forms, even with supplemental water.
The need for supplementary water may be obviated by dispensing liquid medicaments. However, these are messy, as well as difficult to transport and dose properly. Accordingly, efforts have been directed to combining the best features of dry medicaments, for example, tablets, pills, or capsules, such as their ease of transport, accurate dosing, and robust product forms with the best features of liquid medications, such as their ability to be taken without supplemental water and by those with difficulty in swallowing.
Additionally, swallowing oral dosage forms intact implicates a complex system of variables involved in gastrointestinal dissolution of dosage forms and absorption of drugs.
Accordingly, there is considerable interest in oral medicaments and so-called “pre-gastric absorption” of active ingredients. Pre-gastric absorption is the absorption of active ingredients from that part of the alimentary canal prior to the stomach. Pre-gastric absorption thus includes buccal, sublingual, oropharyngeal and esophageal absorption. Medicaments absorbed by such pre-gastric absorption pass straight into the systemic circulatory system, thereby avoiding first pass metabolism in the liver. Accordingly, bioavailability of agents absorbed in this way may also be increased. This means that the dose of such agents may be reduced while still producing the desired beneficial effects, and this decrease in dose may result in a corresponding reduction of unwanted side effects. Current research, as noted in U.S. Pat. No. 6,110,486 to Dugger, shows in particular that absorption through the buccal mucosa represents an often underappreciated route of oral administration that is unavailable to drugs in tablet, pill, or capsule form.
One direction in these efforts has been the development of oral solid pharmaceutical dosage forms that rapidly disintegrate in the mouth. These materials are typically denominated fast dispersing dosage forms. An example is seen in U.S. Pat. No. 5,079,018 to Ecanow, that discloses a fast dispersing dosage form which comprises a porous skeletal structure of a water soluble, hydratable gel or foam forming material which has been hydrated with water. The gel or foam forming material is rigidified in the hydrated state with a rigidifying agent and dehydrated with a liquid organic solvent at a temperature of about 0 degrees C. or below to leave spaces in place of the hydration liquid. Oral solid pharmaceutical dosage forms which rapidly disintegrate in the mouth and methods for their preparation have been proposed in GB A-1548022 and GB-A-2111423. The solid dosage forms as disclosed comprise an open matrix network carrying the pharmaceutically active substance, with the open matrix comprising a water-soluble or water-dispersible carrier material that is inert towards the pharmaceutically active substance. The solid dosage forms are prepared by the sublimation or removal of solvent from a solution or suspension comprising the pharmaceutically active substance and the carrier material. Sublimation or removal of solvent is preferably carried out by freeze-drying, or lyophilization. A typical approach is to dose a drug solution or suspension into free form blisters followed by rapidly freezing the solution or suspension and then freeze-drying. Freeze-drying removes the ice to leave a porous tablet that, when placed on the tongue, disperses in a few seconds. The drug is then swallowed with the saliva. Other methods for preparing oral solid pharmaceutical forms which rapidly disintegrate in the mouth are disclosed in U.S. Pat. Nos. 5,039,540; 5,120,549; and 5,330,763, as well as PCT/JP93/01631 and PCT/U.S.93/12566. Other relevant patents in this technology are U.S. Pat. Nos. 4,760,093; 4,760,094; and 4,767,789.
As seen in the prior art, a typical matrix forming agent is gelatin. Typically, gelatin is used to give sufficient strength to the dosage form to prevent breakage during removal from packaging, but once placed in the mouth, the gelatin allows immediate dispersion of the dosage form. Gelatin, which is normally utilized in such formulations, is defined as a protein obtained by partial hydrolysis of mammalian collagenous tissues, such as skins, tendons, ligaments and bones. Gelatin may also be derived from fish. In comparing gelatin sources, the required heating step of processing mammalian gelatin increases processing time and costs, thereby increasing the overall costs of the process, compared to that for fish gelatin. Additionally, various cultural and religious factors, along with perceptions of health risk in bovine and porcine products, may make fish gelatin more attractive than mammalian gelatin to consumers.
Particularly for pharmaceutical formulations, an advantageous alternative to the use of mammalian derived gelatin is the use of fish gelatin, especially non-gelling fish gelatin. Non-gelling fish gelatin is preferably obtained from cold water fish and has a sol-gel transition temperature, that is, the temperature at which a given solution of gelatin in water, transitions between a liquid and a gel state, that is lower than that of most mammalian derived gelatins. There appears to be a relationship between the temperature at which the animal or fish metabolizes food and the properties of the skin and resultant extracted gelatins.
U.S. Pat. No. 6,709,669 ('669) to Murray teaches the use of a fish gelatin based carrier and an active ingredient, designed for oral and topical dosage forms, as well as a method for lyophilizing, or freeze-drying, and packaging a combination of the active ingredient and the fish gelatin. In a preferred embodiment disclosed in the '669 patent, the composition of the invention is a solid fast-dispersing dosage form containing a network of the active ingredient and a water soluble or water-dispersible carrier comprising fish gelatin (e.g., non-gelling fish gelatin), the network having been formed by subliming solvent from a composition in the solid state containing the active ingredient and a solution or dispersion of the carrier in a solvent.
However, the previous invention of the '669 dosage forms used a commercially available grade of fish gelatin with a molecular weight profile defined by the supplier (Croda Colloids, Ltd.; Cheshire, England). However, gelatin is a naturally occurring, non-homogenous entity, capable of significant variation in chemistry and therefore, considerable variation in physical properties. By way of example and not limitation, experimentation has shown that using a formulation containing certain concentrations of certain grades of fish gelatin, it may not be possible to produce products with a desirable physical robustness and surface appearance. Accordingly, a means has been sought to devise manufacturing methods for fish gelatin products, particularly fast dispersing dosage forms, driven by a quantifiable measurement of at least one chemical property of the gelatin. Ideally, such measurable parameters would improve the ability to prospectively and empirically design a manufacturing protocol with a high degree of commercially effective reproducibility.